As a domain name buyer, one of the toughest replies to respond to is when someone tells me “we need at least $X to sell the domain name.” It makes it seem like the domain registrant is seeking $X for the domain name, but that is not the case. If I increase my offer to $X, there is a strong likelihood they will reject the offer and try to get a better offer. This is probably a good move from their end, but it’s annoying to me as a buyer.
As a domain name seller though, I like this reply. When responding with “we need at least $x to sell the domain name,” I can gauge the seriousness of the other party by how they reply to this. If they make an offer that meets this amount, I can tell them their offer will be considered and then counter at a higher number. If their offer exceeds this minimum, I can see they are very motivated to get a deal done and try for a higher number.
By providing a minimum number and making it clear that it is a minimum a domain seller can tell if the buyer is serious about buying the domain name. It can also buy time for the seller to do some additional research on the domain name to see if it warrants an even higher price than was originally considered. I prefer to keep a prospective buyer engaged rather than biding my time while waiting to respond to an inquiry or offer, so this is a good tactic to stretch out a negotiation without being non-responsive.
One counter argument is that this type of reply could annoy a prospective buyer. The counter party may think the seller is playing games and/or fishing for increasingly better offers. They do have a point to an extent. It’s sort of an evasive answer that gives a bit of a guideline without putting down a firm price. It makes it more difficult for a buyer to pin down the price, and that can frustrate prospects.
Update: Michael made a very good point in the comments about someone misinterpreting this type of response.